Modern Thai Boxing (Muay Thai) originated from Krabi Krabong (a Thai weapons art roughly meaning "stick and sword"). When the Thais lost their weapons or fought close quarters with weapons, they used knees, elbows, feet, fists and headbutting. They became famous for their toughness on the battlefield with constant wars with their Burmese rivals. King Ramkamheng (1275 - 1317) wrote the "Tamrab-Pichei-Songkram" - the Book of War Learning, about the Thai war art, the basis of which was weaponless fighting.

The biggest Thaiboxing hero of Thailand is the 'Black Prince' Nai Khanom Dtom, who was captured by the Burmese and had to fight against 12 of the best Burmese fighters before he was released (in 1560). The Thais still have annual Muay Thai tournaments in order to salute him.

King Naresuan the Great (1555-1605) was a great Thai boxer himself, and he made Muay Thai a required part of military training for all Thai soldiers. Later another Thai king, Phra Chao Seua ( the 'tiger king), further promoted Thai Boxing as a national sport by encouraging prize fights and the development of training camps in the early 18th century. These are accounts of massive wagers and bouts to the death during this time. Phra Chao Seua himself is said to have been an incognito participant in many of the matches during the early part of his reign. Contestants fists were wrapped in thick horsehide for maximum impact with minimum knuckle damage. They also used cotton soaked in glue and ground glass and later hemp bindings. Tree bark and seashells were used to protect the groin from lethal kicks.

Before the 1940's, Thai fighters fought bare-knuckled. In the old days the fights lasted until one of the fighters was dead or seriously injured. There were no rounds, and the fights could have lasted for several hours. After World War II, the Thai government became concerned due to the high number of fatalities in the ring and forced some rules to be used: they gave up groin shots, eye pokes, started using weight classes and boxing gloves, and rounds. The Thais felt that this watered down their sport. As a result, Thais place more emphasis on kicks, particularly to the legs; knee strikes; and grappling. These skills score higher points than hand strikes in Thai matches.